Scalyr output plugin for Fluentd


Note: Fluentd introduced breaking changes to their plugin API between version 0.12 and 0.14.

The current master branch of the scalyr-fluentd plugin is compatible with Fluentd version 0.14 and above, including fluentd v1.0.0.

If you wish to use the scalyr-fluentd plugin with Fluentd version 0.12 or earlier, please use the fluentd-0.12 branch.


The Scalyr output plugin buffers events from fluent and posts them to Scalyr.

Events are uploaded either periodically (e.g. every 5 seconds) or once the buffer reaches a certain size (e.g. 64k).

Fluentd may format log messages into json or some other format. If you want to send raw logs to Scalyr then in your configuration <source> be sure to specify

  format none

The Scalyr output plugin assigns a unique Scalyr session id for each Fluentd <match> block, or for each worker. It is recommended that a single machine doesn't create too many simultaneous Scalyr sessions, so if possible you should try to have a single match for all logs you wish to send to Scalyr.

This can be done by specifying tags such as scalyr.apache, scalyr.maillog etc and matching on scalyr.*

Fluentd tag names will be used for the logfile name in Scalyr.

Plugin Configuration

The Scalyr output plugin has a number of sensible defaults so the minimum configuration only requires your Scalyr 'write logs' token.

<match scalyr.*>
  @type scalyr

The following configuration options are also supported:

<match scalyr.*>
  @type scalyr

  #scalyr specific options
  api_write_token YOUR_SCALYR_WRITE_TOKEN
  compression_type deflate
  compression_level 6
  use_hostname_for_serverhost true
  server_attributes {
    "serverHost": "front-1",
    "serverType": "frontend",
    "region":     "us-east-1"

  ssl_ca_bundle_path /etc/ssl/certs/ca-bundle.crt
  ssl_verify_peer true
  ssl_verify_depth 5
  message_field message
  parser nil

  max_request_buffer 5500000

  force_message_encoding nil
  replace_invalid_utf8 false

  #buffered output options
    retry_max_times 40
    retry_wait 5s
    retry_max_interval 30s
    flush_interval 5s
    flush_thread_count 1
    chunk_limit_size 2.5m
    queue_limit_length 1024


For some additional examples of configuration for different setups, please refer to the examples/configs/ directory.

Scalyr Parsers and Custom Fields

You may also need to specify a Scalyr parser for your log message or add custom fields to each log event. This can be done using Fluentd's filter mechanism, in particular the record_transformer filter.

For example, if you want to use Scalyr's accessLog parser for all events with the scalyr.access tag you would add the following to your fluent.conf file:

<filter scalyr.access>
  @type record_transformer
    parser accessLog

Alternatively, if the same parser can be used for all events sent by the Fluentd output plugin, the parser can be set using the parser plugin configuration. For example, to use Scalyr's accessLog parser for all events, use the output plugin configuration:

<match scalyr.*>
  @type scalyr
  parser accessLog

Scalyr specific options

compression_type - compress Scalyr traffic to reduce network traffic. Options are bz2 and deflate. See here for more details. This feature is optional.

api_write_token - your Scalyr write logs token. See here for more details. This value must be specified.

server_attributes - a JSON hash containing custom server attributes you want to include with each log request. This value is optional and defaults to nil.

use_hostname_for_serverhost - if true then if server_attributes is nil or it does not include a field called serverHost then the plugin will add the serverHost field with the value set to the hostname that fluentd is running on. Defaults to true.

scalyr_server - the Scalyr server to send API requests to. This value is optional and defaults to

ssl_ca_bundle_path - a path on your server pointing to a valid certificate bundle. This value is optional and defaults to nil, which means it will look for a valid certificate bundle on its own.

Note: if the certificate bundle does not contain a certificate chain that verifies the Scalyr SSL certificate then all requests to Scalyr will fail unless ssl_verify_peer is set to false. If you suspect logging to Scalyr is failing due to an invalid certificate chain, you can grep through the Fluentd output for warnings that contain the message 'certificate verification failed'. The full text of such warnings will look something like this:

2015-04-01 08:47:05 -0400 [warn]: plugin/out_scalyr.rb:85:rescue in write: SSL certificate verification failed. Please make sure your certificate bundle is configured correctly and points to a valid file. You can configure this with the ssl_ca_bundle_path configuration option. The current value of ssl_ca_bundle_path is '/etc/ssl/certs/ca-bundle.crt'

2015-04-01 08:47:05 -0400 [warn]: plugin/out_scalyr.rb:87:rescue in write: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed

2015-04-01 08:47:05 -0400 [warn]: plugin/out_scalyr.rb:88:rescue in write: Discarding buffer chunk without retrying or logging to <secondary>

The cURL project maintains CA certificate bundles automatically converted from here.

ssl_verify_peer - verify SSL certificates when sending requests to Scalyr. This value is optional, and defaults to true.

ssl_verify_depth - the depth to use when verifying certificates. This value is optional, and defaults to 5.

message_field - Scalyr expects all log events to have a 'message' field containing the contents of a log message. If your event has the log message stored in another field, you can specify the field name here, and the plugin will rename that field to 'message' before sending the data to Scalyr. Note: this will override any existing 'message' field if the log record contains both a 'message' field and the field specified by this config option.

parser - The Scalyr parser to use to parse the 'message' field for each event. This value is optional and defaults to nil.

max_request_buffer - The maximum size in bytes of each request to send to Scalyr. Defaults to 5,500,000 (5.5MB). Fluentd chunks that generate JSON requests larger than the max_request_buffer will be split in to multiple separate requests. Note: The maximum size the Scalyr servers accept for this value is 6MB and requests containing data larger than this will be rejected.

force_message_encoding - Set a specific encoding for all your log messages (defaults to nil). If your log messages are not in UTF-8, this can cause problems when converting the message to JSON in order to send to the Scalyr server. You can avoid these problems by setting an encoding for your log messages so they can be correctly converted.

replace_invalid_utf8 - If this value is true and force_message_encoding is set to 'UTF-8' then all invalid UTF-8 sequences in log messages will be replaced with <?>. Defaults to false. This flag has no effect if force_message_encoding is not set to 'UTF-8'.

Buffer options

retry_max_times - the maximum number of times to retry a failed post request before giving up. Defaults to 40.

retry_wait - the initial time to wait before retrying a failed request. Defaults to 5 seconds. Wait times will increase up to a maximum of retry_max_interval

retry_max_interval - the maximum time to wait between retrying failed requests. Defaults to 30 seconds. Note: This is not the total maximum time of all retry waits, but rather the maximum time to wait for a single retry.

flush_interval - how often to upload logs to Scalyr. Defaults to 5 seconds.

flush_thread_count - the number of threads to use to upload logs. This is currently fixed to 1 will cause fluentd to fail with a ConfigError if set to anything greater.

chunk_limit_size - the maximum amount of log data to send to Scalyr in a single request. Defaults to 2.5MB. Note: if you set this value too large, then Scalyr may reject your requests. Requests smaller than 6 MB will typically be accepted by Scalyr, but note that the 6 MB limit also includes the entire request body and all associated JSON keys and punctuation, which may be considerably larger than the raw log data. This value should be set lower than the max_request_buffer option.

queue_limit_length - the maximum number of chunks to buffer before dropping new log requests. Defaults to 1024. Combines with chunk_limit_size to give you the total amount of buffer to use in the event of request failures before dropping requests.

Secondary Logging

Fluentd also supports <secondary> logging for all buffered output for when the primary output fails (see the Fluentd documentation for more details). This is also supported by the Scalyr output plugin.

Note: There are certain conditions that may cause the Scalyr plugin to discard a buffer without logging it to secondary output. This will currently happen if:

  • SSL certificate verification fails when sending a request
  • An errant configuration is flooding the Scalyr servers with requests, and the servers respond by dropping/ignoring the logs.



rake build

Which builds the gem and puts it in the pkg directory, then install the Gem using fluent's gem manager

fluent-gem install pkg/fluent-plugin-scalyr-<VERSION>.gem

Publishing a new release to RubyGems

(for project maintainers)

To publish a new version to RubyGems, simply make your changes, make sure all the lint checks and tests pass and merge your changes into master.

After that's done, bump a version in VERSION file, update file, add a tag which matches a version in VERSION file (e.g. v0.8.10) and push that tag to the remote:

git tag v0.8.10
git push origin v0.8.10

Push of this tag will trigger a Circle CI job which will build the latest version of the gem and publish it to RubyGems.